Should I forgive my friend for losing my cat?

Hi. I (24f), recently went on vacation for 2 weeks with my boyfriend. As a bit of a background, I own a dog and a cat. My dog is old, very chill, and a good boy, so I wasn't too worried about him. My cat, however, is only 2 years old, and she's a rescue. When I rescued her a year and a half ago, I was informed she was the victim of animal abuse, and as a result one of her legs has problems. It's been hard raising her because as a result of the abuse she went through, she's extremely skiddish and jumpy. I've owned her for a year and a half and she hesitates to even let ME pet her, let alone anyone else. She mostly just runs away from other people, except for my boyfriend who she's mostly warmed up to, as well.

Onto the actual issue at hand... When I went on vacation, I asked a close friend of mine, Kelly(26f), who lives literally a 30 second walk away from my house, to watch over my cat and dog. Kelly has been one of my best friends for about 10 years. I love her a lot.

I didn't want to put either of my pets in a boarding facility for a few reasons:

A) money is tight and those aren't cheap

B) my dog is old and has arthritis in his back legs. I want him comfy in his own environment

C) my cat is already always stressed and anxious; a boarding facility would be a nightmare for her

Before entrusting my babies to Kelly, I made sure she was comfortable and up to the task. She has a dog herself, so all she had to do for my dog was take him on walks with her dog, and feed him. As for the cat, she just had to clean the litter box and feed her. Easy.

I checked up with her every single day while I was on vacation, both to remind her to do her duties and to ensure everything was going okay because I was nervous. Every time she responded that it was no problem and everything was cool.

I returned home about 10 days ago, and she was waiting for me. She confessed to me that my cat had ran out the door a week into my trip. She had left the door open accidentally when coming in to clean the litter box and feed them. For context, my front door is a bit broken. The part that clicks shut sticks sometimes, and doesnt pop back out, so you have to actually rotate the handle to make sure its closed. I showed her how to do it before I left, and made it very clear she has to make sure it actually closes, then lock it. I made this VERY clear, to the point where she even joked "yeah, yeah, I got it... relax" and rolled her eyes sarcastically.

When my cat ran out, Kelly followed her and tried to get her back. At one point she managed to pick the cat up, but because she's so skiddish, she ended up thrashing and scratching Kellys arms, and she had to drop her, at which point she ran away under a fence and she lost her (Kelly has the marks to prove it). She said she looked for her since, but she didn't put up missing posters or anything. She lied to me for the last week of my vacation that everything was going fine, and her justification for this was that she didn't want to stress me out unnecessarily while I was on vacation. I freaked out and yelled at her and we had a big argument that included Kelly asserting that she tried to get her back, and me arguing that she shouldn't have left the door open to begin with and that she was irresponsible. I also said I wish she would've just told me, and that she should've put up posters. I would've even made them! She could've just printed and posted them to poles. We haven't talked since.

I put up missing posters and have been looking, but its now been almost 20 days since the day she escaped and ran away. I hate to say it, but I've pretty much lost any hope that she's coming back, or is even alive at this point. I'm not sure how long a 2 year old cat with a bad hip can last all by herself, especially in my area (we have foxes and coyotes frequently).

Aside from feeling obviously sad and devestated that I may never see her again, or even know what happened to her, I'm also very angry at Kelly. I havent been able to forgive her. I talked to my boyfriend about it, but obviously he's going to take my side. I really miss my kitty, but I also miss my friend. I know she made a mistake and she didn't do anything purposefully to hurt me, but I'm still mad at her irresponbility. It sucks and idk what to do or say to her.

TL;DR my friend agreed to catsit for me, she left my door open, my cat got out and I can't find her. Now I'm mad at her.

I need an outside perspective, so please, I need any advice on how to handle this, if I should forgive her, etc. I will appreciate any advice; it's really hard to focus on anything else right now.

Thank you in advance.